Organic light emitting display apparatus and method of manufacturing the organic light emitting display apparatus

ABSTRACT

An organic light-emitting display apparatus includes a substrate including a plurality of red, green, and blue sub-pixel regions, a pixel electrode in each of the plurality of the red, green, and blue sub-pixel regions on the substrate, a Distributed Bragg Reflector (DBR) layer between the substrate and the pixel electrodes, a high-refractive index layer between the substrate and the DBR layer in the blue sub-pixel region, the high-refractive index layer having a smaller area than an area of a corresponding pixel electrode in the blue sub-pixel region, an intermediate layer including an emissive layer on the pixel electrode, and an opposite electrode on the intermediate layer.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of Korean Patent Application No.10-2011-0134464, filed on Dec. 14, 2011, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND

1. Field

An aspect of example embodiments relates to an organic light emittingdisplay apparatus and a method of manufacturing the organic lightemitting display apparatus.

2. Description of the Related Art

Display apparatuses are recently being replaced by thin flat paneldisplay apparatuses that are portable. Organic light-emitting displayapparatuses from among flat panel display apparatuses are self-emissiondisplay apparatuses and have a larger viewing angle, better contrastcharacteristics, and a faster response rate than other displayapparatuses, and thus have drawn attention as next-generation displayapparatuses.

Organic light emitting display apparatuses have an intermediate layer, afirst electrode, and a second electrode. The intermediate layer includesan organic emission layer, and the organic emission layer generatesvisible light when the first electrode and the second electrode aresupplied with a voltage.

SUMMARY

Example embodiments provide an organic light emitting display apparatusand a method of manufacturing the organic light emitting displayapparatus, by which emission properties of blue light may be improved.

According to an aspect of the example embodiment, there is provided anorganic light-emitting display apparatus, including a substrateincluding a plurality of red, green, and blue sub-pixel regions, a pixelelectrode in each of the plurality of the red, green, and blue sub-pixelregions on the substrate, a Distributed Bragg Reflector (DBR) layerbetween the substrate and the pixel electrodes, a high-refractive indexlayer between the substrate and the DBR layer in the blue sub-pixelregion, the high-refractive index layer having a smaller area than anarea of a corresponding pixel electrode in the blue sub-pixel region, anintermediate layer including an emissive layer on the pixel electrode,and an opposite electrode on the intermediate layer.

The DBR layer may be formed by alternately stacking a first layer and asecond layer that have different refractive indices.

The refractive index of the first layer may be smaller than therefractive index of the second layer.

The first layer may be formed of silicon oxide and the second layer maybe formed of silicon nitride.

The high-refractive index layer may have a refractive index greater thanthe refractive index of the DBR layer.

The high-refractive index layer may be formed of polysilicon.

The organic light-emitting display apparatus may further include anauxiliary layer interposed between the substrate and the DBR layer.

The auxiliary layer may be formed of silicon oxide.

The high-refractive index layer may be disposed on the auxiliary layer.

According to another aspect of the example embodiment, there is providedan organic light-emitting display apparatus including a thin filmtransistor (TFT) on a substrate, the TFT having an active layer, a gateelectrode insulated from the active layer, the gate electrode includinga lower gate electrode and an upper gate electrode, an interlayerinsulation layer covering the gate electrode, and a source electrode anda drain electrode on the interlayer insulation layer, the source anddrain electrodes contacting the active layer, an organic light-emittingdevice on the substrate, the organic light-emitting device including astacked structure of a pixel electrode electrically connected to theTFT, an intermediate layer including an emissive layer, and an oppositeelectrode, a DBR layer between the active layer and the gate electrodeof the TFT, and a high-refractive index layer between the substrate andthe DBR layer, the high-refractive index layer having a smaller area anarea of the pixel electrode.

The high-refractive index layer may be disposed on the substrate so asto face the pixel electrode of a blue sub-pixel for emitting blue light,the pixel electrode included in the organic light-emitting device.

The high-refractive index layer may have a refractive index greater thana refractive index of the DBR layer.

The high-refractive index layer may be formed of polysilicon.

The organic light-emitting display apparatus may further include anauxiliary layer interposed between the substrate and the DBR layer.

The auxiliary layer may be formed of silicon oxide.

The high-refractive index layer may be disposed on the auxiliary layer.

The DBR layer may be formed by alternately stacking a first layer and asecond layer that have different refractive indices.

The refractive index of the first layer may be smaller than therefractive index of the second layer.

The first layer may be formed of silicon oxide and the second layer maybe formed of silicon nitride.

The high-refractive index layer may be formed of a material same as amaterial used to form the active layer.

The high-refractive index layer may be disposed on the same layer as thelayer on which the active layer is formed.

The organic light-emitting display apparatus may further include acapacitor comprising a lower capacitor electrode formed in the samelayer as the layer in which the active layer is formed and an uppercapacitor electrode formed on the DBR layer, the capacitor electricallycoupled to the TFT.

The high-refractive index layer may be disposed on the same layer as thelayer on which the active layer and the lower capacitor electrode areformed.

The high-refractive index layer may be formed of the same material as amaterial used to form the active layer and the lower capacitorelectrode.

According to another aspect of the example embodiment, there is provideda method of manufacturing an organic light-emitting display apparatusincluding a first mask process of forming an active layer of a TFT and ahigh-refractive index layer on a substrate, a second mask process offorming a gate electrode of the TFT and a first electrode unit forforming a pixel electrode on the substrate, a third mask process offorming an interlayer insulation layer, the interlayer insulation layerincluding contact holes exposing edges of the active layer and a holeexposing a part of the first electrode unit, a fourth mask process offorming a source electrode and a drain electrode that contact the activelayer via the contact holes and forming the pixel electrode from thefirst electrode unit, and a fifth mask process of forming a pixeldefinition layer exposing at least a part of the pixel electrode.

The first mask process may include: forming an amorphous silicon layeron the substrate, forming a polysilicon layer by crystallizing theamorphous silicon layer, and forming the active layer and thehigh-refractive index layer by patterning the polysilicon layer.

Before the forming of the amorphous silicon layer, the method mayfurther include forming an auxiliary layer on the substrate, wherein theactive layer and the high-refractive index layer are disposed on theauxiliary layer.

The second mask process may include: forming a DBR layer on thesubstrate to cover the active layer and the high-refractive index layer,sequentially forming a first conductive layer and a second conductivelayer on the DBR layer, and forming the gate electrode including thefirst conductive layer as a lower gate electrode and the secondconductive layer as an upper gate electrode, by patterning the firstconductive layer and the second conductive layer.

The DBR layer may be formed by alternately stacking a first layer and asecond layer that have different refractive indices.

The refractive index of the first layer may be smaller than therefractive index of the second layer.

The first layer may be formed of silicon oxide and the second layer maybe formed of silicon nitride.

The high-refractive index layer may have a refractive index greater thana refractive index of the DBR layer.

The first mask process may further include: forming a lower capacitorelectrode on the substrate in the same layer as the layer in which theactive layer and the high-refractive index layer are formed, and formingan upper capacitor electrode over the lower capacitor electrode.

In the second mask process, the DBR layer may be formed on the substrateto cover the lower capacitor electrode.

The fourth mask process may include: forming a third conductive layer onthe interlayer insulation layer, forming the source electrode and thedrain electrode by patterning the third conductive layer, and forming apixel electrode comprising the first conductive layer, by removing thesecond conductive layer constituting the first electrode unit.

The third mask process may include: forming an intermediate layer on thefirst electrode unit and the gate electrode, and forming a hole viawhich a part of the first electrode unit is exposed, and the contactholes, by patterning the interlayer insulation layer.

The fifth mask process may include: forming an insulation layer on anentire surface of the substrate to cover the source electrode and thedrain electrode, and forming the pixel definition layer by patterningthe insulation layer.

After the fifth mask process, the method may further include forming anintermediate layer comprising an emissive layer, and an oppositeelectrode on an upper surface of the pixel electrode.

The high-refractive index layer may be formed on the substrate so as tocorrespond to the pixel electrode.

The high-refractive index layer may be formed to be smaller than thepixel electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the example embodimentswill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings, in which:

FIG. 1 is a schematic cross-sectional view of an organic light emittingdisplay apparatus according to an embodiment;

FIG. 2 is a schematic cross-sectional view of an organic light emittingdisplay apparatus according to another embodiment; and

FIGS. 3 through 10 are cross-sectional views of stages in a method ofmanufacturing the organic light emitting display apparatus shown in FIG.2.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings, in which aspects of embodiments are shown. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items. Expressions such as “at leastone of,” when preceding a list of elements, modify the entire list ofelements and do not modify the individual elements of the list.

FIG. 1 is a cross-sectional view of an organic light emitting displayapparatus 100 according to an embodiment. Referring to FIG. 1, theorganic light-emitting display apparatus 100 includes a first substrate10 a and red (R), green (G), and blue (B) sub-pixel regions R, G, and Bformed on the first substrate 10 a.

The first substrate 10 a may be, for example, a transparent glasssubstrate, a plastic substrate, or a metal foil. In another example, asubstrate which is used in organic light emitting display apparatuseshaving a high mechanical strength, high thermal stability, hightransparency, high surface smoothness, high handling easiness, and ahigh waterproof property may be used as the first substrate 10 a. Asillustrated in FIG. 1, the first substrate 10 a may include at least onethin film transistor (TFT) and/or at least one capacitor in each of theR, G, and B sub-pixel regions R, G, and B, and the TFT and the capacitormay constitute a pixel circuit.

A second substrate 10 b may be an encapsulation substrate disposed onthe first substrate 10 a to protect the TFTs, light-emitting pixels, andthe like formed on the first substrate 10 a from external moisture, air,and the like. The second substrate 10 b is positioned to face the firstsubstrate 10 a, and the first substrate 10 a and the second substrate 10b are joined together by a sealing member (not shown) disposed along theedge of the second substrate 10 b. The second substrate 10 b may be,e.g., a glass substrate or a plastic substrate.

An auxiliary layer 11, for example, a barrier layer, a blocking layer,and/or a buffer layer, may be formed on an upper surface of the firstsubstrate 10 a to prevent diffusion of impurity ions and penetration ofmoisture or external air and to planarize the upper surface of the firstsubstrate 10 a. The auxiliary layer 11 may be formed using, for example,SiO₂ and/or SiN_(x), according to any of various deposition methods, forexample, plasma enhanced chemical vapor deposition (PECVD), atmosphericpressure CVD (APCVD), and low pressure CVD (LPCVD). For example, theauxiliary layer 11 formed of SiO₂ may have a thickness in the range ofabout 300 Å to about 400 Å.

A distributed Bragg reflector (DBR) layer 12 may be formed on, e.g.,directly on, the auxiliary layer 11. The DBR layer 12 may be formed bystacking a first layer 12 a and a second layer 12 b on, e.g., directlyon, the auxiliary layer 11, e.g., the first layer 12 a may be betweendirectly between the auxiliary layer 11 and the second layer 12 b. Thefirst layer 12 a and the second layer 12 b have different refractiveindices. For example, the refractive index of the first layer 12 a maybe smaller than that of the second layer 12 b. For example, the firstlayer 12 a may be formed of silicon oxide (SiO_(x)), and the secondlayer 12 b may be formed of silicon nitride (SiN_(x)). Although thefirst layer 12 a and the second layer 12 b are stacked in FIG. 1, theexample embodiments are not limited thereto, and the first layer 12 aand the second layer 12 b may be stacked alternately with each other inthree or more layers.

Since a layer having a small refractive index (for example, the firstlayer 12 a) and a layer having a large refractive index (for example,the auxiliary layer 11 and the second layer 12 b) alternate with eachother, the auxiliary layer 11 and the DBR layer 12 generate resonancedue to a difference between their refractive indices. Thus, lightefficiency and color purity may be improved.

A high-refractive index layer 19 may be formed in the B sub-pixel regionB to be interposed between the auxiliary layer 11 and the DBR layer 12,e.g., the high-refractive index layer 19 may be interposed between theauxiliary layer 11 and the first layer 12 a. The high-refractive indexlayer 19 has a refractive index greater than that of the DBR layer 12,e.g., a refractive index greater than either of the first and secondlayers 12 a and 12 b. The high-refractive index layer 19 may be formedof, e.g., polysilicon.

The high-refractive index layer 19 may be disposed in the B sub-pixelregion B and may be formed to have an area less than that of a bluepixel electrode 43B. For example, the blue pixel electrode 43B mayoverlap the entire high-refractive index layer 19, and thehigh-refractive index layer 19 may overlap only a portion of the bluepixel electrode 43B. For example, a part of the blue pixel electrode43B, i.e., a region B1, includes the DBR layer 12 without thehigh-refractive index layer 19, and another part of the blue pixelelectrode 43B (a region B2 in FIG. 1), e.g., a remaining part of theblue pixel electrode 43B, includes both the DBR layer 12 and thehigh-refractive index layer 19. Since weak resonance is generated by theDBR layer 12 in the region B1, the luminance of blue light and a Moirephenomenon may be improved. In the region B2 including thehigh-refractive index layer 19, since the high-refractive index layer 19has a refractive index higher than that that of the DBR layer 12, colorreproducibility of blue light may be improved.

First electrodes 43R, 43G, and 43B and a second electrode 45 that faceeach other are formed above the first substrate 10 a. The firstelectrodes 43R, 43G, and 43B may be formed in R, G, and B subpixels,respectively, and may be an anode or a cathode. The second electrode 45may functions as an anode or a cathode by corresponding to the firstelectrodes 43R, 43G, and 43B. The second electrode 45 may be formed onintermediate layers 44R, 44G, and 44B by vacuum deposition, sputtering,or the like.

When the organic light-emitting display apparatus 100 is a bottomemission type displaying an image toward the first substrate 10 a, thefirst electrodes 43R, 43G, and 43B may be transparent electrodes and thesecond electrode 45 is a reflective electrode. The first electrodes 43R,43G, and 43B may be formed of, for example, ITO, IZO, ZnO, or In₂O₃having a high work function, and the second electrode 45 may be formedof a metal having a low work function such as silver (Ag), magnesium(Mg), aluminum (Al), platinum (Pt), palladium (Pd), gold (Au), nickel(Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), or acompound or alloy of these materials.

When the organic light-emitting display apparatus 100 is a dual emissiontype, the first electrodes 43R, 43G, and 43B and the second electrode 45may be all transparent electrodes.

When the first substrate 10 a includes TFTs as described above, thefirst electrodes 43R, 43G, and 43B formed in corresponding sub-pixelsmay be electrically connected to TFTs of the sub-pixels, respectively.In this case, the second electrode 45 may be formed of a commonelectrode that extends across all subpixels.

When the first substrate 10 a includes no TFTs in each sub-pixel, thefirst electrodes 43R, 43G, and 43B and the second electrode 45 areformed in strips so that the first electrodes 43R, 43G, and 43Bintersect the second electrode 45, and thus may be driven in a PassiveMatrix (PM) manner.

The intermediate layers 44R, 44G, and 44B may be interposed between thefirst electrode 43R and the second electrode 45, between the firstelectrode 43G and the second electrode 45, and between the firstelectrode 43B and the second electrode 45, respectively. Theintermediate layers 44R, 44G, and 44B may be formed by stacking anorganic emissive layer (EML) and at least one functional layer of a holeinjection layer (HIL), a hole transport layer (HTL), an electrontransport layer (ETL), and an electron injection layer (EIL).

Pixel defining layers 16 may be formed on the first electrodes 43R, 43G,and 43B so as to cover upper ends and lateral surfaces of the firstelectrodes 43R, 43G, and 43B. The pixel defining layers 16 may have anorganic material multi-layered structure, an inorganic materialmulti-layered structure, or an inorganic/organic material complexmulti-layered structure. Silicon oxide (SiO₂), silicon nitride(SiN_(x)), silicon oxynitride, or the like may be used as an inorganicmaterial used to form the pixel defining layers 16. An organicinsulation material, such as an acryl-based organic compound, polyimide,or polyamide may be used as an organic material used to form the pixeldefining layers 16.

FIG. 2 is a schematic cross-sectional view of an organic light emittingdisplay apparatus 1 according to another embodiment. Referring to FIG.2, the organic light-emitting display apparatus 1 includes a firstsubstrate 10 including a plurality of light-emitting pixels, and asecond substrate (not shown) attached to the first substrate 10 bysealing.

A TFT, an organic light-emitting diode (EL), a capacitor Cst, and thelike may be formed on the first substrate 10. The first substrate 10 maybe, e.g., a low temperature polycrystalline silicon (LTPS) substrate, aglass substrate, a plastic substrate, or the like.

The second substrate may be an encapsulation substrate disposed on thefirst substrate 10 to protect the TFT, the light-emitting pixels, andthe like formed on the first substrate 10 from external moisture, air,and the like. The second substrate is positioned to face the firstsubstrate 10, and the first substrate 10 and the second substrate arejoined together by a sealing member (not shown) disposed along the edgeof the second substrate. The second substrate may be, e.g., a glasssubstrate or a plastic substrate.

The organic light-emitting display apparatus 1 is divided into atransistor region 2, a storage region 3, and a light-emitting region 4,on the first substrate 10. The light-emitting region 4 of FIG. 2represents a B sub-pixel region.

The auxiliary layer 11, for example, a barrier layer, a blocking layer,and/or a buffer layer, may be formed on an upper surface of the firstsubstrate 10 to prevent diffusion of impurity ions and penetration ofmoisture or external air and to planarize the upper surface of the firstsubstrate 10. The auxiliary layer 11 may be formed of SiO₂.

The transistor region 2 includes the TFT serving as a driving device.The TFT includes an active layer 21, a gate electrode 20, a sourceelectrode 29, and a drain electrode 27.

The gate electrode 20 includes a lower gate electrode 23 and an uppergate electrode 25 formed on an upper surface of the lower gate electrode23. The lower gate electrode 23 may be formed of a transparentconductive material. Examples of the transparent conductive material mayinclude at least one of indium tin oxide (ITO), indium zinc oxide (IZO),zinc oxide (ZnO), indium oxide (In₂O₃), indium gallium oxide (IGO), andaluminum zinc oxide (AZO). The upper gate electrode 25 may have asingle- or multi-layered structure including a metal or a metal alloy,such as Mo, MoW, or an Al-based alloy.

The DBR layer 12 is interposed between the gate electrode 20 and theactive layer 21 to insulate the gate electrode 21 from the active layer21. The DBR layer 12 may be formed by stacking the first layer 12 a andthe second layer 12 b. The first layer 12 a and the second layer 12 bhave different refractive indices. For example, the refractive index ofthe first layer 12 a may be smaller than that of the second layer 12 b.The first layer 12 a may be formed of silicon oxide (SiO_(x)), and thesecond layer 12 b may be formed of silicon nitride (SiN_(x)). Althoughthe first layer 12 a and the second layer 12 b are stacked in FIG. 2,the first layer 12 a and the second layer 12 b may be stackedalternately with each other in three or more layers.

Since a layer having a small refractive index (for example, the firstlayer 12 a) and a layer having a large refractive index (for example,the auxiliary layer 11 and the second layer 12 b) alternate with eachother, the auxiliary layer 11 and the DBR layer 12 generate resonancedue to a difference between the refractive indices of these layers andthus may improve light efficiency and color purity.

The high-refractive index layer 19 may be formed in the light-emittingregion 4 as a B sub-pixel region to be interposed between the auxiliarylayer 11 and the DBR layer 12. The high-refractive index layer 19 may beinterposed between the auxiliary layer 11 and the first layer 12 a. Thehigh-refractive index layer 19 has a refractive index greater than thatof the DBR layer 12. The high-refractive index layer 19 may be formed onthe same layer as, e.g., at a same distance from an upper surface of thesubstrate 10 as, the layer on which the active layer 21 of the TFT isformed. The high-refractive index layer 19 may be formed of a samematerial, e.g., same polysilicon, as the active layer 21.

The high-refractive index layer 19 may be disposed in the B sub-pixelregion 4 and may be formed to have an area less than that of a bluepixel electrode 43B. For example, a part of the light-emitting region 4as the B sub-pixel region includes the DBR layer 12 without thehigh-refractive index layer 19, and the remaining part of thelight-emitting region 4 includes both the DBR layer 12 and thehigh-refractive index layer 19. Since weak resonance is generated by theDBR layer 12 in the part of the light-emitting region 4 including theDBR layer 12 without the high-refractive index layer 19, the luminanceof blue light and a Moiré phenomenon may be improved. In the part of thelight-emitting region 4 including the high-refractive index layer 19,since the high-refractive index layer 19 has a refractive index higherthan that that of the DBR layer 12, the color reproducibility of bluelight may be improved.

A source area 21 s and a drain area 21 d doped with highly-concentratedimpurities are formed on both edges, respectively, of the active layer21, and are connected to the source and drain electrodes 29 and 27,respectively.

The storage region 3 includes the capacitor Cst. The capacitor Cstincludes a lower capacitor electrode 31 and an upper capacitor electrode33, and the DBR layer 12 is interposed between the lower capacitorelectrode 31 and the upper capacitor electrode 33. The lower capacitorelectrode 31 may be formed on the same layer as the layer on which theactive layer 21 of the TFT is formed. The lower capacitor electrode 31is formed of a semiconductor material, and is doped with impurities toincrease electrical conductivity. The upper capacitor electrode 33 maybe formed on the same layer as the layer on which the lower gateelectrode 23 of the TFT and the blue pixel electrode 43B, whichconstitutes the EL, are formed. In other words, the upper capacitorelectrode 33 may be formed of a transparent conductive material, likethe lower gate electrode 23.

The light-emitting region 4 includes the EL. The EL includes the bluepixel electrode 43B connected to the source or drain electrode 29 or 27of the TFT, an opposite electrode 45 formed to face the blue pixelelectrode 43B, and an intermediate layer 44B interposed between the bluepixel electrode 43B and the opposite electrode 45. The blue pixelelectrode 43B may be formed of a transparent conductive material, or maybe formed of the same material as that used to form the lower gateelectrode 23 or the like on the same layer as that on which the lowergate electrode 23 or the like is formed.

FIGS. 3 through 10 are cross-sectional views of stages in a method ofmanufacturing the organic light emitting display apparatus 1 of FIG. 2.The method of manufacturing the organic light emitting display apparatus1 of FIG. 2 will now be described schematically.

First, as shown in FIG. 2, the auxiliary layer 11 is formed on the firstsubstrate 10. For example, the first substrate 10 may be formed of atransparent glass material containing SiO₂ as a main component. However,the first substrate 10 is not limited thereto. The first substrate 10may be any substrate formed of various materials, for example, atransparent plastic, a metal, or the like.

The auxiliary layer 11, for example, a barrier layer, a blocking layer,and/or a buffer layer, may be formed on an upper surface of the firstsubstrate 10 to prevent diffusion of impurity ions and penetration ofmoisture or external air and to planarize the upper surface of the firstsubstrate 10. The auxiliary layer 11 may be formed using, for example,SiO₂ and/or SiN_(x), according to any of various deposition methods, forexample, PECVD, APCVD, and LPCVD.

Next, as shown in FIG. 3, the high-refractive index layer 19, the activelayer 21 of the TFT, and the lower capacitor electrode 31 are formed onan upper surface of the auxiliary layer 11. In detail, an amorphoussilicon layer (not shown) is first formed on the upper surface of theauxiliary layer 11 and then crystallized to generate a polycrystallinesilicon layer (not shown). Amorphous silicon may be crystallized usingany of various methods such as rapid thermal annealing (RTA), solidphase crystallization (SPC), excimer laser annealing (ELA), metalinduced crystallization (MIC), metal induced lateral crystallization(MILC), and sequential lateral solidification (SLS). The polycrystallinesilicon layer is patterned, e.g., simultaneously, to form thehigh-refractive index layer 19, the active layer 21 of the TFT, and thelower capacitor electrode 31 in respective regions 4, 2, and 3, by usinga mask process using a first mask (not shown). It is noted that althoughthe active layer 21 and the lower capacitor electrode 31 are separatedfrom each other in the present embodiment, the active layer 21 and thelower capacitor electrode 31 may be integrally formed.

Next, as shown in FIG. 4, the DBR layer 12, a first conductive layer(not shown), and a second conductive layer (not shown) are sequentiallyformed on the entire surface of the first substrate 10 on which thehigh-refractive index layer 19, the active layer 21, and the lowercapacitor electrode 31 have been formed.

The DBR layer 12 is formed by stacking the first layer 12 a and thesecond layer 12 b. The first layer 12 a and the second layer 12 b havedifferent refractive indices. For example, the refractive index of thefirst layer 12 a may be less than that of the second layer 12 b. Thefirst layer 12 a may be formed of silicon oxide (SiO_(x)), and thesecond layer 12 b may be formed of silicon nitride (SiN_(x)). Althoughthe first layer 12 a and the second layer 12 b are stacked in FIG. 4,the first layer 12 a and the second layer 12 b may be stackedalternately with each other in three or more layers.

Since a layer having a small refractive index (for example, the firstlayer 12 a) and a layer having a large refractive index (for example,the second layer 12 b) alternate with each other, the DBR layer 12generate resonance due to a difference between the refractive indices ofthese layers and thus may improve light efficiency and color purity.

The DBR layer 12 may be formed according to a method such as PECVD,APCVD, or LPCVD. The DBR layer 12 is disposed between the active layer21 and the gate electrode 20 of the TFT to serve as a gate insulationlayer of the TFT, and also disposed between the upper capacitorelectrode 33 and the lower capacitor electrode 31 to serve as adielectric layer of the capacitor Cst.

The first conductive layer (not shown) may include at least onetransparent material, e.g., at least one of ITO, IZO, ZnO, and In₂O₃.Thereafter, the first conductive layer may be patterned to form the bluepixel electrode 43B, the lower gate electrode 23, and the uppercapacitor electrode 33.

The second conductive layer (not shown) may include at least one ofsilver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), palladium(Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium(Cr), lithium (Li), calcium (Ca), molybdenum (Mo), titanium (Ti),tungsten (W), MoW, and copper (Cu). For example, the second conductivelayer may have a three-layered structure, e.g., a Mo/Al/Mo structure. Itis noted, however, that the first conductive layer may include a highcorrosion-resistant material compared to the second conductive layer, sothe second conductive layer may include a material that has lessresistance than the material of the first conductive layer to smoothlytransmit a current.

Next, as illustrated in FIG. 5, the first and second conductive layersmay be patterned to form the gate electrode 20 in region 2, a firstelectrode unit 40 in region 4, and a second electrode unit 30 in region3 of the first substrate 10. In detail, the first conductive layer andthe second conductive layer sequentially stacked on the entire surfaceof the first substrate 10 may be patterned according to a mask processusing a second mask (not shown).

The gate electrode 20 is formed over the active layer 21 in thetransistor region 2 and includes the lower gate electrode 23 formed of apart of the first conductive layer and the upper gate electrode 25formed of a part of the second conductive layer. The gate electrode 20is formed to be aligned with the center of the active layer 21, and theactive layer 21 is doped with n-type or p-type impurities by using thegate electrode 20 as a self-aligned mask to form the source and drainareas 21 s and 21 d on an edge of the active layer 21 corresponding toboth sides of the gate electrode 20 and to form a channel area 21 cbetween the source/drain areas 21 s and 21 d. The impurities may beboron (B) ions or phosphorus (P) ions.

The second electrode unit 30 for forming the upper capacitor electrode33 is formed over the lower capacitor electrode 31 in the storage region3, and the first electrode unit 40 for forming the blue pixel electrode43B is formed in the light-emitting region 4. For example, the secondconductive layer is patterned to form simultaneously the second gateelectrode 25 with a second patterned conductive layer on each of theupper capacitor electrode 33 and the blue pixel electrode 43B.

Next, as illustrated in FIG. 6, an interlayer insulation layer 14 isformed on the entire surface of the first substrate 10 on which the gateelectrode 20 has been formed. For example, the interlayer insulationlayer 14 is formed of at least one organic insulation material, e.g., atleast one of polyimide, polyamide, acryl resin, benzocyclobutene (BCB)and a phenolic resin by using a method such as spin coating. Theinterlayer insulation layer 14 is formed to have a sufficient thickness,for example, to be thicker than the DBR layer 12, and insulates the gateelectrode 20 of the TFT from the source and drain electrodes 29 and 27of the TFT. The interlayer insulation layer 14 may be formed of not onlythe above-described organic insulation material, but also of aninorganic insulation material such as the above-described inorganicmaterial used to form the DBR layer 12. Alternatively, the interlayerinsulation layer 14 may be formed by alternating an organic insulationmaterial with an inorganic insulation material.

Next, as illustrated in FIG. 7, the interlayer insulation layer 14 ispatterned to form holes (a third hole H3, a fourth hole H4, and a fifthhole H5) exposing the second and first electrode unit 30 and 40 andcontact holes (a first hole H1 and a second hole H2) exposing parts ofthe source and drain areas 21 s and 21 d of the active layer 21.

In detail, the interlayer insulation layer 14 is patterned according toa mask process using a third mask (not shown) to thereby form thecontact holes H1 and H2 and the holes H3, H4, and H5. The first hole H1and the second hole H2 expose parts of the source and drain areas 21 sand 21 d, respectively, and the third hole H3 and the fourth hole H4expose at least a part of the first electrode unit 40. The fifth hole H5exposes at least a part of the second electrode unit 30.

Next, as illustrated in FIG. 8, a third conductive layer 17 is formed onthe entire surface of the first substrate 10 so as to cover theinterlayer insulation layer 14. The third conductive layer 17 may beformed of one of the conductive materials used to form the first andsecond conductive layers, but the third conductive layer 17 is notlimited thereto and may be formed of any of various other suitableconductive materials. The selected conductive material is deposited to asufficient thickness enough to fill the contact holes H1 and H2 and theholes H3, H4, and H5.

Next, as illustrated in FIG. 9, the third conductive layer 17 of FIG. 8is patterned to form the source and drain electrodes 29 and 27 and toexpose the blue pixel electrode 43B and the upper capacitor electrode33. In detail, the fourth conductive layer 17 of FIG. 8 is patternedaccording to a mask process using a fourth mask (not shown) to therebyform the source and drain electrodes 29 and 27.

One electrode selected from the source and drain electrodes 29 and 27(for example, the drain electrode 27 in FIG. 9) is formed to contact theblue pixel electrode 43B via the third hole H3 in an edge area of thesecond conductive layer corresponding to an upper portion of the firstelectrode unit 40 of FIG. 7 in which the blue pixel electrode 43B is tobe formed.

The blue pixel electrode 43B and the upper capacitor electrode 33 areformed at the same time when the source and drain electrodes 29 and 27are formed. However, the example embodiments are not limited thereto,and the blue pixel electrode 43B and the upper capacitor electrode 33may be formed via additional etching after the source and drainelectrodes 29 and 27 are formed. In detail, the blue pixel electrode 43Bmay be formed by removing a portion of the second conductive layerthereon exposed via the fourth hole H4. The upper capacitor electrode 33may be formed by removing a portion of the second conductive layerexposed via the third hole H3.

The lower gate electrode 23, the upper capacitor electrode 33, and theblue pixel electrode 43B are formed of the same material.

The lower capacitor electrode 31 may be doped by injecting n-type orp-type impurities thereinto via the fifth hole H5. The impurities usedfor the above-described doping may be identical to or different fromthose used to dope the active layer 21.

Next, as illustrated in FIG. 10, a pixel definition layer (PDL) 16 isformed on the first substrate 10. In detail, the PDL 16 is formed on theentire surface of the first substrate 10 on which the blue pixelelectrode 43B, the source and drain electrodes 29 and 27, and the uppercapacitor electrode 33 have been formed. For example, the PDL 16 may beformed of at least one organic insulation material, e.g., at least oneof polyimide, polyamide (PA), acryl resin, benzocyclobutene (BCB) and aphenolic resin by using a method such as spin coating. In anotherexample, the PDL 16 may be formed of, e.g., only, an inorganicinsulation material, e.g., at least one of SiO₂, SiN_(x), Al₂O₃,CuO_(x), Tb₄O₇, Y₂O₃, Nb₂O₅, Pr₂O₃, and TiOx. In yet another example,the PDL 16 may have a multi-layered structure by alternating an organicinsulation material with an inorganic insulation material.

The PDL 16 is patterned according to a mask process using a fifth mask(not shown) to thereby form a sixth hole H6 exposing a center portion ofthe blue pixel electrode 43B. In this way, a pixel is defined.

Thereafter, as illustrated in FIG. 2, the intermediate layer 44Bincluding an emission layer, and the opposite electrode 45 are formed inthe sixth hole H6 exposing the blue pixel electrode 43B.

The intermediate layer 44B may be formed by stacking an organic emissivelayer (EML) and at least one of a hole injection layer (HIL), a holetransport layer (HTL), an electron transport layer (ETL), and anelectron injection layer (EIL). The organic EML may be formed of alow-molecular weight organic material or a high-molecular weight organicpolymer.

When the organic EML is formed of the low-molecular weight organicmaterial, the intermediate layer 44B is obtained by stacking the HTL,the HIL, and the like on a surface of the organic EML facing the bluepixel electrode 43B, and the ETL, the EIL, and the like on a surface ofthe organic EML facing the opposite electrode 45. Various other suitablelayers may be stacked if necessary. Examples of organic materials thatmay be used to form the organic EML include any of various suitablematerials, e.g., copper phthalocyanine (CuPc),N,N′-Di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB), andtris-8-hydroxyquinoline aluminum (Alq3).

On the other hand, when the organic emissive layer is formed of ahigh-molecular weight organic polymer, the intermediate layer 44B may beformed by stacking only a HTL on the surface of the organic EML facingthe blue pixel electrode 43B. The HTL may be formed ofpoly-(3.4)-ethylene-dihydroxy thiophene (PEDOT), polyaniline (PANI), orthe like on the upper surface of the blue pixel electrode 43B by inkjetprinting or spin coating. High-molecular weight organic polymers, e.g.,polyphenylenevinylenes (PPVs) and polyfluorenes, may be used as theorganic polymers forming the organic EML. A color pattern may be formedby using a typical method such as inkjet printing, spin coating, or athermal transfer method using a laser.

The opposite electrode 45 may be formed on the entire surface of thefirst substrate 10 so as to serve as a common electrode. In the organiclight-emitting display apparatus 1 according to the present embodiment,the blue pixel electrode 43B is used as an anode electrode, and theopposite electrode 45 is used as a cathode electrode. Alternatively, theblue pixel electrode 43B may be used as a cathode electrode, and theopposite electrode 45 may be used as an anode electrode.

When the organic light-emitting display apparatus 1 is a bottom emissiontype displaying an image toward the first substrate 10, the blue pixelelectrode 43B is a transparent electrode and the opposite electrode 45is a reflective electrode. The reflective electrode may be formed bythinly depositing a metal having a low work function, such as Ag, Mg,Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF/Ca, LiF/Al, or a combinationthereof.

A removal of a stacked layer during each mask process performed to forman organic light emitting display apparatus may be achieved by dryetching or wet etching.

In a bottom-emission type display apparatus and a manufacturing methodthereof according to an embodiment, a resonance structure may berealized by the DBR layer 12, and in particular, light characteristicsof blue light, such as luminance and color reproducibility, may beimproved by the high-refractive index layer 19 formed to be smaller thana B sub-pixel region. Since the bottom-emission type display apparatushaving this structure is manufactured using only five (5) masks, themanufacturing of an organic light-emitting display apparatus may besimplified and the manufacturing costs thereof may be reduced.

Although an organic light-emitting display apparatus is illustrated inthe above-described embodiment, the example embodiments are not limitedthereto, and various suitable display devices including a liquid crystaldisplay (LCD) may be used.

Although a single TFT and a single capacitor are illustrated in theabove-described embodiment, this illustration is only for convenience ofexplanation, and the example embodiments are not limited thereto. Aslong as the number of mask processes used is not increased, a pluralityof TFTs and a plurality of capacitors may be included. As such, thenumber of masks to be used is reduced, as compared to conventionalmethods, and emission properties of blue light may be improved.

While the example embodiments has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the example embodiments as defined by the following claims.

What is claimed is:
 1. An organic light-emitting display apparatus,comprising: a substrate including a plurality of red, green, and bluesub-pixel regions; a pixel electrode in each of the plurality of thered, green, and blue sub-pixel regions on the substrate; a DistributedBragg Reflector (DBR) layer between the substrate and the pixelelectrodes; a high-refractive index layer between the substrate and theDBR layer in the blue sub-pixel region, the high-refractive index layerhaving a smaller area than an area of a corresponding pixel electrode inthe blue sub-pixel region; an intermediate layer including an emissivelayer on the pixel electrode; and an opposite electrode on theintermediate layer.
 2. The organic light-emitting display apparatus ofclaim 1, wherein the DBR layer includes a first layer and a second layerstacked on each other, the first and second layers having differentrefractive indices.
 3. The organic light-emitting display apparatus ofclaim 2, wherein the refractive index of the first layer is smaller thanthe refractive index of the second layer.
 4. The organic light-emittingdisplay apparatus of claim 2, wherein the first layer includes siliconoxide and the second layer includes silicon nitride.
 5. The organiclight-emitting display apparatus of claim 1, wherein the high-refractiveindex layer has a refractive index greater than the refractive index ofthe DBR layer.
 6. The organic light-emitting display apparatus of claim1, wherein the high-refractive index layer includes polysilicon.
 7. Theorganic light-emitting display apparatus of claim 1, further comprisingan auxiliary layer interposed between the substrate and the DBR layer.8. The organic light-emitting display apparatus of claim 7, wherein theauxiliary layer includes silicon oxide.
 9. The organic light-emittingdisplay apparatus of claim 7, wherein the high-refractive index layer ison the auxiliary layer.
 10. An organic light-emitting display apparatus,comprising: a thin film transistor (TFT) on a substrate, the TFTincluding: an active layer, a gate electrode insulated from the activelayer, the gate electrode including a lower gate electrode and an uppergate electrode, an interlayer insulation layer covering the gateelectrode, and a source electrode and a drain electrode on theinterlayer insulation layer, the source and drain electrodes contactingthe active layer; an organic light-emitting device on the substrate, theorganic light-emitting device including a stacked structure of a pixelelectrode electrically connected to the TFT, an intermediate layerincluding an emissive layer, and an opposite electrode; a DBR layerbetween the active layer and the gate electrode of the TFT; and ahigh-refractive index layer between the substrate and the DBR layer, thehigh-refractive index layer having a smaller area an area of the pixelelectrode.
 11. The organic light-emitting display apparatus of claim 10,wherein the high-refractive index layer faces a pixel electrode of ablue sub-pixel.
 12. The organic light-emitting display apparatus ofclaim 10, wherein the high-refractive index layer has a refractive indexgreater than a refractive index of the DBR layer.
 13. The organiclight-emitting display apparatus of claim 10, wherein thehigh-refractive index layer includes polysilicon.
 14. The organiclight-emitting display apparatus of claim 10, further comprising anauxiliary layer interposed between the substrate and the DBR layer. 15.The organic light-emitting display apparatus of claim 14, wherein theauxiliary layer includes silicon oxide.
 16. The organic light-emittingdisplay apparatus of claim 14, wherein the high-refractive index layeris between the auxiliary layer and the DBR layer.
 17. The organiclight-emitting display apparatus of claim 10, wherein the DBR layerincludes alternately stacked first and second layers, the first andsecond layers having different refractive indices.
 18. The organiclight-emitting display apparatus of claim 17, wherein the refractiveindex of the first layer is smaller than the refractive index of thesecond layer.
 19. The organic light-emitting display apparatus of claim17, wherein the first layer includes silicon oxide and the second layerincludes silicon nitride.
 20. The organic light-emitting displayapparatus of claim 10, wherein the high-refractive index layer includesa same material as the active layer of the TFT.
 21. The organiclight-emitting display apparatus of claim 10, wherein thehigh-refractive index layer is directly on a same layer as the activelayer of the TFT.
 22. The organic light-emitting display apparatus ofclaim 10, further comprising a capacitor including a lower capacitorelectrode in on a same layer as the active layer and an upper capacitorelectrode on the DBR layer, the capacitor being electrically coupled tothe TFT.
 23. The organic light-emitting display apparatus of claim 22,wherein the high-refractive index layer is on a same layer as the activelayer and the lower capacitor electrode.
 24. The organic light-emittingdisplay apparatus of claim 22, wherein the high-refractive index layerincludes a same material as the active layer and the lower capacitorelectrode.
 25. A method of manufacturing an organic light-emittingdisplay apparatus, the method comprising: a first mask process offorming an active layer of a TFT and a high-refractive index layer on asubstrate; a second mask process of forming a gate electrode of the TFTand a first electrode unit for forming a pixel electrode on thesubstrate; a third mask process of forming an interlayer insulationlayer, the interlayer insulation layer including contact holes exposingedges of the active layer and a hole exposing a part of the firstelectrode unit; a fourth mask process of forming a source electrode anda drain electrode that contact the active layer via the contact holesand forming the pixel electrode from the first electrode unit; and afifth mask process of forming a pixel definition layer exposing at leasta part of the pixel electrode.
 26. The method of claim 25, wherein thefirst mask process includes: forming an amorphous silicon layer on thesubstrate; forming a polysilicon layer by crystallizing the amorphoussilicon layer; and forming simultaneously the active layer and thehigh-refractive index layer by patterning the polysilicon layer.
 27. Themethod of claim 26, further comprising, before forming the amorphoussilicon layer, forming an auxiliary layer on the substrate, the activelayer and the high-refractive index layer being disposed on theauxiliary layer.
 28. The method of claim 25, wherein the second maskprocess includes: forming a DBR layer on the substrate to cover theactive layer and the high-refractive index layer; sequentially forming afirst conductive layer and a second conductive layer on the DBR layer;and forming the gate electrode including the first conductive layer as alower gate electrode and the second conductive layer as an upper gateelectrode, by patterning the first conductive layer and the secondconductive layer.
 29. The method of claim 28, wherein the DBR layer isformed by alternately stacking a first layer and a second layer thathave different refractive indices.
 30. The method of claim 29, whereinthe refractive index of the first layer is smaller than the refractiveindex of the second layer.
 31. The method of claim 29, wherein the firstlayer is formed of silicon oxide and the second layer is formed ofsilicon nitride.
 32. The method of claim 28, wherein the high-refractiveindex layer has a refractive index greater than a refractive index ofthe DBR layer.
 33. The method of claim 28, wherein the first maskprocess further comprises: forming a lower capacitor electrode on thesubstrate in the same layer as the layer in which the active layer andthe high-refractive index layer are formed; and forming an uppercapacitor electrode over the lower capacitor electrode.
 34. The methodof claim 33, wherein, in the second mask process, the DBR layer isformed on the substrate to cover the lower capacitor electrode.
 35. Themethod of claim 28, wherein the fourth mask process includes: forming athird conductive layer on the interlayer insulation layer; forming thesource electrode and the drain electrode by patterning the thirdconductive layer; and forming a pixel electrode including the firstconductive layer, by removing the second conductive layer constitutingthe first electrode unit.
 36. The method of claim 25, wherein the thirdmask process includes: forming an intermediate layer on the firstelectrode unit and the gate electrode; and forming a hole exposing apart of the first electrode unit and contact holes, by patterning theinterlayer insulation layer.
 37. The method of claim 25, wherein thefifth mask process includes: forming an insulation layer on an entiresurface of the substrate to cover the source electrode and the drainelectrode; and forming the pixel definition layer by patterning theinsulation layer.
 38. The method of claim 25, further comprising, afterthe fifth mask process, forming an intermediate layer including anemissive layer, and an opposite electrode on an upper surface of thepixel electrode.
 39. The method of claim 25, wherein the high-refractiveindex layer is formed on the substrate so as to correspond to the pixelelectrode.
 40. The method of claim 25, wherein the high-refractive indexlayer is formed to be smaller than the pixel electrode.